To promote and maintain health, all healthy adults aged 18–65 yr need moderate-intensity aerobic physical activity for a minimum of 30 min on five days each week or vigorous-intensity aerobic activity for a minimum of 20 min on three days each week (WILLIAM L. HASKELL1, 2007). Again, this information is too subjective for not only the general public, but also for fitness professionals. Many of us have heard of the benefits of High-Intensity-Interval-Training (HIIT). This relatively new paradigm in cardiovascular training has been proven to be superior to continuous or long-slow-distance (LSD) training with respect to total calorie and fat calorie expenditure in a much lesser time commitment. I’m a believer in HIIT and its effectiveness and reduction in the amount of overuse injuries that are commonly associated with many longer duration aerobic activities (i.e. running). To further investigate this issue, I found several studies advocating HIIT.
High-intensity interval training (HIIT) continues to outpace the competition. In a study published in the Journal of Applied Physiology, researchers had subjects perform eight sessions of cardio on exercise bikes using either a HUT protocol C20 minutes of total cardio with one minute of high-intensity intervals at 120% of aerobic capacity followed by one minute of rest] or a traditional cardio model [90-120minutes of total cardio at 65% of maximal aerobic capacity). In just 19 days, numerous performance benefits were seen in both groups, including maximal aerobic capacity relative to bodyweight and increased time to fatigue during an exhaustive exercise test, as well as improvements in oxygen delivery to muscle and the ability to delay lactate accumulation in both groups. Perhaps the most striking finding is that all these improvements occurred in the HUT group after only 80 minutes of work. Compare this to the 825 minutes it took the endurance group to get the same results and you have a solid HUT endorsement (GO AHEAD, HIIT YOURSELF, Sept. 2009).
Now the question is, does HIIT have similar benefits in preventing cardiovascular disease as continuous moderate aerobic activity? In a study investigating the cardiovascular benefits of interval training, the results of this study suggest that 8 weeks of high-intensity interval training can elicit favorable changes in HDL-C and the lipoprotein ratio in young adult men. Specifically, we observed an 18% increase in HDL-C, similar to increases previously reported with endurance training, but there was no change in TC. It was not surprising to observe that TC did not change significantly with training, given that exercise produces reciprocal changes in TC, especially with regard to HDL-C and low-density lipoprotein cholesterol (LDL-C). In most studies, as HDL-C increases, LDL-C decreases, and this leads to either no change or a slight reduction in TC. Furthermore, because the subjects in the present study had favorable pre-training mean TC levels, there was less room for further reduction in cholesterol levels (Musa, Adeniran, Dikko, & Sayers, March 2009) .
With this information at hand, this provides the fitness professional with another means to effectively train their client’s cardiovascular system while efficiently training for weight and fat loss. On another note, it should be said that HIIT is not for everyone and proper progressive aerobic training should precede HIIT.
GO AHEAD, HIIT YOURSELF. (Sept. 2009). Joe Weider’s Muscle & Fitness , 56.
Musa, D. I., Adeniran, S. A., Dikko, A. U., & Sayers, S. P. (March 2009). The Effect of a High-Intensity Interval Training Program on High-Density Lipoprotein Cholesterol in Young Men. Journal of Strength and Conditioning Research , 587-592.
WILLIAM L. HASKELL1, I.-M. L. (2007). Physical Activity and Public Health: Updated Recommendation for Adults from the ACSM and AHA. Official Journal of the American College of Sports Medicine , 1423-1434.